NC 18 is a 145-mile (233 km) North Carolina state highway that travels north–south through the Foothills and Mountain regions of the state.

NC 18's northern terminus is at NC 89, just shy of the North Carolina/Virginia state line near the independent city of Galax, Virginia. From this point, NC 18 travels in a westerly direction (signed south) for approximately one-half mile before meeting the Blue Ridge Parkway at the Surry/Alleghany county line.

From the Blue Ridge Parkway, NC 18 continues westerly to the town of Sparta. Traveling through the heart of the town, NC 18 crosses US 21, and then exits Sparta in a more southerly direction. Curving through the Blue Ridge Mountains, NC 18 meets the termini of NC 113 and NC 88 in the small community of Laurel Springs. Shortly after crossing the Blue Ridge Parkway again, NC 18 hugs the Ashe/Alleghany county line before entering Wilkes County.

NC 18 curves around the mountainous terrain and continues south into Mulberry and then North Wilkesboro. NC 268 joins NC 18 (and later US 421 Business) through the town of North Wilkesboro, where both routes are also known at various points as Second Street, Main Street, and Wilkesboro Boulevard. After crossing the Yadkin River into Wilkesboro, NC 18 and NC 268 wind through the town's streets (Wilkesboro Avenue, East Main Street), splitting near the center of town; NC 18 continues south as South Cherry Street. Joining with NC 16 at a junction with the US 421 Bypass freeway, the routes exit the town to the south. Arriving in the community of Moravian Falls, NC 18 splits from NC 16 to the southwest. NC 18 hugs the Yadkin River and southern shores of the W. Kerr Scott Reservoir on its way to Lenoir in Caldwell County.

Entering the city of Lenoir as Wilkesboro Boulevard, NC 18 joins US 64 through the heart of the city. The two routes cross US 321 (Hickory Boulevard), turn left onto Morganton Boulevard, cross US 321 Alternate (Norwood Street), and continue through downtown. US 64 and NC 18 stay joined after exiting Lenoir, through the town of Gamewell, and after exiting Caldwell County.

Entering Burke County, US 64 and NC 18 bypass Rhodhiss Lake and enter into the city of Morganton. Shortly crossing the Catawba River, US 64 splits between a bypass route and a business route. NC 18 follows US 64 Business and Lenoir Road into downtown Morganton. After sharing Lenoir Street and Avery Avenue, both routes meet a terminus of NC 118, and then split between two one-way streets: Green Street and Sterling Street. In downtown, US 64 Business joins US 70 Business, while NC 18 continues southeasterly. After crossing a few railroad tracks, both streets join into a normal 2-lane road still known as Sterling Street. The state highway then meets US 70 and eventually arrives at an interchange with Interstate 40 (exit 105). Exiting Morganton, NC 18 travels through rural Burke County to the Catawba County line.

Shortly after entering Catawba County, NC 18 exits it, entering into Lincoln County. There, in the small community of Laurel Hill, NC 18 meets NC 10 and NC 27 before entering Cleveland County. Heading in a nearly due south direction, NC 18 travels through Belwood and Fallston, where it intersects with NC 182. Further south, the route meets the northern terminus of NC 180 before entering the city of Shelby. Routed along the city streets of Fallston Road, Grover Street, and Lafayette Street, NC 18 crosses US 74 Business and joins NC 150. After crossing US 74 Bypass/NC 226, both NC 150 and NC 18 exit the city to the south before splitting shortly after. NC 18 then heads due south, picking up NC 180 on its way to the South Carolina border, where both routes terminate; SC 18 begins at this terminus, near the town of Earl, North Carolina.